Nix/src/libutil/args.cc

#include "args.hh"
#include "args/root.hh"
#include "hash.hh"
#include "environment-variables.hh"
#include "signals.hh"
#include "users.hh"
#include "json-utils.hh"

#include <fstream>
#include <string>
#include <regex>
#include <glob.h>

namespace nix {

void Args::addFlag(Flag && flag_)
{
    auto flag = std::make_shared<Flag>(std::move(flag_));
    if (flag->handler.arity != ArityAny)
        assert(flag->handler.arity == flag->labels.size());
    assert(flag->longName != "");
    longFlags[flag->longName] = flag;
    for (auto & alias : flag->aliases)
        longFlags[alias] = flag;
    if (flag->shortName) shortFlags[flag->shortName] = flag;
}

void Args::removeFlag(const std::string & longName)
{
    auto flag = longFlags.find(longName);
    assert(flag != longFlags.end());
    if (flag->second->shortName) shortFlags.erase(flag->second->shortName);
    longFlags.erase(flag);
}

void Completions::setType(AddCompletions::Type t)
{
    type = t;
}

void Completions::add(std::string completion, std::string description)
{
    description = trim(description);
    // ellipsize overflowing content on the back of the description
    auto end_index = description.find_first_of(".\n");
    if (end_index != std::string::npos) {
        auto needs_ellipsis = end_index != description.size() - 1;
        description.resize(end_index);
        if (needs_ellipsis)
            description.append(" [...]");
    }
    completions.insert(Completion {
        .completion = completion,
        .description = description
    });
}

bool Completion::operator<(const Completion & other) const
{ return completion < other.completion || (completion == other.completion && description < other.description); }

std::string completionMarker = "___COMPLETE___";

RootArgs & Args::getRoot()
{
    Args * p = this;
    while (p->parent)
        p = p->parent;

    auto * res = dynamic_cast<RootArgs *>(p);
    assert(res);
    return *res;
}

std::optional<std::string> RootArgs::needsCompletion(std::string_view s)
{
    if (!completions) return {};
    auto i = s.find(completionMarker);
    if (i != std::string::npos)
        return std::string(s.begin(), i);
    return {};
}

void RootArgs::parseCmdline(const Strings & _cmdline)
{
    // Default via 5.1.2.2.1 in C standard
    Args::parseCmdline("", _cmdline);
}

void Args::parseCmdline(const std::string & programName, const Strings & _cmdline)
{
    Strings pendingArgs;
    bool dashDash = false;

    Strings cmdline(_cmdline);

    if (auto s = getEnv("NIX_GET_COMPLETIONS")) {
        size_t n = std::stoi(*s);
        assert(n > 0 && n <= cmdline.size());
        *std::next(cmdline.begin(), n - 1) += completionMarker;
        completions = std::make_shared<Completions>();
        verbosity = lvlError;
    }

    bool argsSeen = false;

    // Heuristic to see if we're invoked as a shebang script, namely,
    // if we have at least one argument, it's the name of an
    // executable file, and it starts with "#!".
    Strings savedArgs;
    auto isNixCommand = std::regex_search(programName, std::regex("nix$"));
    if (isNixCommand && cmdline.size() > 0) {
        auto script = *cmdline.begin();
        try {
            std::ifstream stream(script);
            char shebang[3]={0,0,0};
            stream.get(shebang,3);
            if (strncmp(shebang,"#!",2) == 0){
                for (auto pos = std::next(cmdline.begin()); pos != cmdline.end();pos++)
                    savedArgs.push_back(*pos);
                cmdline.clear();

                std::string line;
                std::getline(stream,line);
                std::string commentChars("#/\\%@*-");
                while (std::getline(stream,line) && !line.empty() && commentChars.find(line[0]) != std::string::npos){
                    line = chomp(line);

                    std::smatch match;
                    if (std::regex_match(line, match, std::regex("^#!\\s*nix\\s(.*)$")))
                        for (const auto & word : shellwords(match[1].str()))
                            cmdline.push_back(word);
                }
                cmdline.push_back(script);
                for (auto pos = savedArgs.begin(); pos != savedArgs.end();pos++)
                    cmdline.push_back(*pos);
            }
        } catch (SysError &) { }
    }
    for (auto pos = cmdline.begin(); pos != cmdline.end(); ) {

        auto arg = *pos;

        /* Expand compound dash options (i.e., `-qlf' -> `-q -l -f',
           `-j3` -> `-j 3`). */
        if (!dashDash && arg.length() > 2 && arg[0] == '-' && arg[1] != '-' && isalpha(arg[1])) {
            *pos = (std::string) "-" + arg[1];
            auto next = pos; ++next;
            for (unsigned int j = 2; j < arg.length(); j++)
                if (isalpha(arg[j]))
                    cmdline.insert(next, (std::string) "-" + arg[j]);
                else {
                    cmdline.insert(next, std::string(arg, j));
                    break;
                }
            arg = *pos;
        }

        if (!dashDash && arg == "--") {
            dashDash = true;
            ++pos;
        }
        else if (!dashDash && std::string(arg, 0, 1) == "-") {
            if (!processFlag(pos, cmdline.end()))
                throw UsageError("unrecognised flag '%1%'", arg);
        }
        else {
            if (!argsSeen) {
                argsSeen = true;
                initialFlagsProcessed();
            }
            pos = rewriteArgs(cmdline, pos);
            pendingArgs.push_back(*pos++);
            if (processArgs(pendingArgs, false))
                pendingArgs.clear();
        }
    }

    processArgs(pendingArgs, true);

    if (!argsSeen)
        initialFlagsProcessed();

    /* Now that we are done parsing, make sure that any experimental
     * feature required by the flags is enabled */
    for (auto & f : flagExperimentalFeatures)
        experimentalFeatureSettings.require(f);

    /* Now that all the other args are processed, run the deferred completions.
     */
    for (auto d : deferredCompletions)
        d.completer(*completions, d.n, d.prefix);
}

bool Args::processFlag(Strings::iterator & pos, Strings::iterator end)
{
    assert(pos != end);

    auto & rootArgs = getRoot();

    auto process = [&](const std::string & name, const Flag & flag) -> bool {
        ++pos;

        if (auto & f = flag.experimentalFeature)
            rootArgs.flagExperimentalFeatures.insert(*f);

        std::vector<std::string> args;
        bool anyCompleted = false;
        for (size_t n = 0 ; n < flag.handler.arity; ++n) {
            if (pos == end) {
                if (flag.handler.arity == ArityAny || anyCompleted) break;
                throw UsageError(
                    "flag '%s' requires %d argument(s), but only %d were given",
                    name, flag.handler.arity, n);
            }
            if (auto prefix = rootArgs.needsCompletion(*pos)) {
                anyCompleted = true;
                if (flag.completer) {
                    rootArgs.deferredCompletions.push_back({
                        .completer = flag.completer,
                        .n = n,
                        .prefix = *prefix,
                    });
                }
            }
            args.push_back(*pos++);
        }
        if (!anyCompleted)
            flag.handler.fun(std::move(args));
        return true;
    };

    if (std::string(*pos, 0, 2) == "--") {
        if (auto prefix = rootArgs.needsCompletion(*pos)) {
            for (auto & [name, flag] : longFlags) {
                if (!hiddenCategories.count(flag->category)
                    && hasPrefix(name, std::string(*prefix, 2)))
                {
                    if (auto & f = flag->experimentalFeature)
                        rootArgs.flagExperimentalFeatures.insert(*f);
                    rootArgs.completions->add("--" + name, flag->description);
                }
            }
            return false;
        }
        auto i = longFlags.find(std::string(*pos, 2));
        if (i == longFlags.end()) return false;
        return process("--" + i->first, *i->second);
    }

    if (std::string(*pos, 0, 1) == "-" && pos->size() == 2) {
        auto c = (*pos)[1];
        auto i = shortFlags.find(c);
        if (i == shortFlags.end()) return false;
        return process(std::string("-") + c, *i->second);
    }

    if (auto prefix = rootArgs.needsCompletion(*pos)) {
        if (prefix == "-") {
            rootArgs.completions->add("--");
            for (auto & [flagName, flag] : shortFlags)
                if (experimentalFeatureSettings.isEnabled(flag->experimentalFeature))
                    rootArgs.completions->add(std::string("-") + flagName, flag->description);
        }
    }

    return false;
}

bool Args::processArgs(const Strings & args, bool finish)
{
    if (expectedArgs.empty()) {
        if (!args.empty())
            throw UsageError("unexpected argument '%1%'", args.front());
        return true;
    }

    auto & rootArgs = getRoot();

    auto & exp = expectedArgs.front();

    bool res = false;

    if ((exp.handler.arity == ArityAny && finish) ||
        (exp.handler.arity != ArityAny && args.size() == exp.handler.arity))
    {
        std::vector<std::string> ss;
        bool anyCompleted = false;
        for (const auto &[n, s] : enumerate(args)) {
            if (auto prefix = rootArgs.needsCompletion(s)) {
                anyCompleted = true;
                ss.push_back(*prefix);
                if (exp.completer) {
                    rootArgs.deferredCompletions.push_back({
                        .completer = exp.completer,
                        .n = n,
                        .prefix = *prefix,
                    });
                }
            } else
                ss.push_back(s);
        }
        if (!anyCompleted)
            exp.handler.fun(ss);

        /* Move the list element to the processedArgs. This is almost the same as 
           `processedArgs.push_back(expectedArgs.front()); expectedArgs.pop_front()`,
           except that it will only adjust the next and prev pointers of the list
           elements, meaning the actual contents don't move in memory. This is
           critical to prevent invalidating internal pointers! */
        processedArgs.splice(
            processedArgs.end(),
            expectedArgs,
            expectedArgs.begin(),
            ++expectedArgs.begin());

        res = true;
    }

    if (finish && !expectedArgs.empty() && !expectedArgs.front().optional)
        throw UsageError("more arguments are required");

    return res;
}

nlohmann::json Args::toJSON()
{
    auto flags = nlohmann::json::object();

    for (auto & [name, flag] : longFlags) {
        auto j = nlohmann::json::object();
        j["hiddenCategory"] = hiddenCategories.count(flag->category) > 0;
        if (flag->aliases.count(name)) continue;
        if (flag->shortName)
            j["shortName"] = std::string(1, flag->shortName);
        if (flag->description != "")
            j["description"] = trim(flag->description);
        j["category"] = flag->category;
        if (flag->handler.arity != ArityAny)
            j["arity"] = flag->handler.arity;
        if (!flag->labels.empty())
            j["labels"] = flag->labels;
        j["experimental-feature"] = flag->experimentalFeature;
        flags[name] = std::move(j);
    }

    auto args = nlohmann::json::array();

    for (auto & arg : expectedArgs) {
        auto j = nlohmann::json::object();
        j["label"] = arg.label;
        j["optional"] = arg.optional;
        if (arg.handler.arity != ArityAny)
            j["arity"] = arg.handler.arity;
        args.push_back(std::move(j));
    }

    auto res = nlohmann::json::object();
    res["description"] = trim(description());
    res["flags"] = std::move(flags);
    res["args"] = std::move(args);
    auto s = doc();
    if (s != "") res.emplace("doc", stripIndentation(s));
    return res;
}

static void hashTypeCompleter(AddCompletions & completions, size_t index, std::string_view prefix)
{
    for (auto & type : hashTypes)
        if (hasPrefix(type, prefix))
            completions.add(type);
}

Args::Flag Args::Flag::mkHashTypeFlag(std::string && longName, HashType * ht)
{
    return Flag {
        .longName = std::move(longName),
        .description = "hash algorithm ('md5', 'sha1', 'sha256', or 'sha512')",
        .labels = {"hash-algo"},
        .handler = {[ht](std::string s) {
            *ht = parseHashType(s);
        }},
        .completer = hashTypeCompleter,
    };
}

Args::Flag Args::Flag::mkHashTypeOptFlag(std::string && longName, std::optional<HashType> * oht)
{
    return Flag {
        .longName = std::move(longName),
        .description = "hash algorithm ('md5', 'sha1', 'sha256', or 'sha512'). Optional as can also be gotten from SRI hash itself.",
        .labels = {"hash-algo"},
        .handler = {[oht](std::string s) {
            *oht = std::optional<HashType> { parseHashType(s) };
        }},
        .completer = hashTypeCompleter,
    };
}

static void _completePath(AddCompletions & completions, std::string_view prefix, bool onlyDirs)
{
    completions.setType(Completions::Type::Filenames);
    glob_t globbuf;
    int flags = GLOB_NOESCAPE;
    #ifdef GLOB_ONLYDIR
    if (onlyDirs)
        flags |= GLOB_ONLYDIR;
    #endif
    // using expandTilde here instead of GLOB_TILDE(_CHECK) so that ~<Tab> expands to /home/user/
    if (glob((expandTilde(prefix) + "*").c_str(), flags, nullptr, &globbuf) == 0) {
        for (size_t i = 0; i < globbuf.gl_pathc; ++i) {
            if (onlyDirs) {
                auto st = stat(globbuf.gl_pathv[i]);
                if (!S_ISDIR(st.st_mode)) continue;
            }
            completions.add(globbuf.gl_pathv[i]);
        }
    }
    globfree(&globbuf);
}

void Args::completePath(AddCompletions & completions, size_t, std::string_view prefix)
{
    _completePath(completions, prefix, false);
}

void Args::completeDir(AddCompletions & completions, size_t, std::string_view prefix)
{
    _completePath(completions, prefix, true);
}

Strings argvToStrings(int argc, char * * argv)
{
    Strings args;
    argc--; argv++;
    while (argc--) args.push_back(*argv++);
    return args;
}

std::optional<ExperimentalFeature> Command::experimentalFeature ()
{
    return { Xp::NixCommand };
}

MultiCommand::MultiCommand(const Commands & commands_)
    : commands(commands_)
{
    expectArgs({
        .label = "subcommand",
        .optional = true,
        .handler = {[=,this](std::string s) {
            assert(!command);
            auto i = commands.find(s);
            if (i == commands.end()) {
                std::set<std::string> commandNames;
                for (auto & [name, _] : commands)
                    commandNames.insert(name);
                auto suggestions = Suggestions::bestMatches(commandNames, s);
                throw UsageError(suggestions, "'%s' is not a recognised command", s);
            }
            command = {s, i->second()};
            command->second->parent = this;
        }},
        .completer = {[&](AddCompletions & completions, size_t, std::string_view prefix) {
            for (auto & [name, command] : commands)
                if (hasPrefix(name, prefix))
                    completions.add(name);
        }}
    });

    categories[Command::catDefault] = "Available commands";
}

bool MultiCommand::processFlag(Strings::iterator & pos, Strings::iterator end)
{
    if (Args::processFlag(pos, end)) return true;
    if (command && command->second->processFlag(pos, end)) return true;
    return false;
}

bool MultiCommand::processArgs(const Strings & args, bool finish)
{
    if (command)
        return command->second->processArgs(args, finish);
    else
        return Args::processArgs(args, finish);
}

nlohmann::json MultiCommand::toJSON()
{
    auto cmds = nlohmann::json::object();

    for (auto & [name, commandFun] : commands) {
        auto command = commandFun();
        auto j = command->toJSON();
        auto cat = nlohmann::json::object();
        cat["id"] = command->category();
        cat["description"] = trim(categories[command->category()]);
        cat["experimental-feature"] = command->experimentalFeature();
        j["category"] = std::move(cat);
        cmds[name] = std::move(j);
    }

    auto res = Args::toJSON();
    res["commands"] = std::move(cmds);
    return res;
}

}